1. Field of the Disclosure
Embodiments of the present disclosure generally relate to a heat-assisted magnetic recording (HAMR) head and a method for manufacturing the HAMR head
2. Description of the Related Art
HAMR, sometimes referred to as thermally-assisted magnetic recording (TAMR or TAR) or energy assisted magnetic recording (EAMR), is a process whereby a localized area on the magnetic media is heated to a temperature above the Curie temperature, thereby lowering the effective coercivity of the localized region. The lowered coercivity permits writing within this heated region. The data state becomes “fixed” once the media cools below the Curie temperature.
HAMR heads typically have a light source, such as a laser diode, that delivers the light through a waveguide and a near field transducer (NFT) to focus the energy on a very specific location. The light source is disposed adjacent to the write head on a surface opposite the air bearing surface (ABS). The light source is coupled to a submount, which is mounted to the slider.
The submount is typically soldered to the slider. All the solder materials used for attaching the submount to the slider consist of metal films or film stacks that will alloy, melt, and wet the mating surfaces after being heated to the appropriate temperature during bonding (for brevity, this will be referred to simply as ‘melting’ the solder hereafter). In particular, solders are sought that will melt at low temperatures, so that: (a) the components can be heated quickly enough to enable high throughput in the soldering/bonding operation; and (b) the heating does not cause damage to either the slider or the submount.
Typically, heat is conducted to the solder through the slider body, for example by contact with a chuck that is heated electrically, or by a laser pointed at the chuck. Heat can also be conducted in through the submount, for example by directing a laser onto the submount. An additional proposal has been to heat the solder directly using a laser to whose wavelength the submount material is transparent. Alternatively, another proposal is to heat the solder using a pin probe that passes a small electrical current across the solder, or across an embedded thin film resistive heater embedded under the solder.
The above described existing technologies all share one common feature—the energy used for melting the solder is supplied in full from an external source, with none of the energy carried within the solder itself. As a consequence, the full energy supply for the bonding operation must be: (1) provided via some mechanism in the bonding apparatus which is not itself required for bonding; and (2) delivered through one or both of the submount and slider, in order to perform bonding.
The speed of the bonding operation is affected by how quickly the energy can be transferred. In the case of conduction through the submount or slider, the heat flux is described by Fick's Laws, in which the flux of heat is directly proportional to the temperature gradient between the bonding surface of the component and the surface to which the heat is applied. For a given component, accelerating the solder melting can only be achieved by using higher temperatures, which takes more time and poses more risk of misalignment due to thermal expansion, thermal drift, and other factors. Additionally, higher temperatures pose more risk of damage to the component.
Proposed technologies based on direct laser heating through a ‘transparent’ submount do not depend on conduction, but still depend on optical transmission of the full melting energy through the submount. To perform such heating, the size of the laser required and the risk that reflected light will cause either inefficient or undesirable heating is quite large. In particular, heating by such a method runs the risk of impinging light onto the laser-submount joint, thereby destroying the alignment of the laser on the submount.
Proposals based on embedded electrical heating are a further step towards maximally efficient use of the energy provided during bonding, by ensuring that nearly all the heat is delivered to the solder instead of the components. However, in all these prior art cases, the energy provided must still be the full energy of bonding. In all these cases, additional features must be designed into the bonding apparatus, such as chuck heaters, special heating lasers, pin probes, etc. As long as the full energy of bonding is provided, bonding will never be as fast or as safe as if only a fraction of the energy needed to be supplied. This is possible only if the remaining energy is stored within the solder itself in the form of chemical potential energy. As long as additional components are required for the bonding apparatus, it will never be as cost-effective or reliable as a simpler system in which only the basic alignment and bonding features are included.
Therefore, there is a need in the art for a faster, cheaper method of bonding a submount to a slider in a HAMR head, and a HAMR head produced thereof.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.